1. Field of the Invention
This invention pertains generally to the field of combustion engines and more particularly to combustion engines capable of operating on diverse fuels. In general, modifications are made to a combustion engine so that it is capable of operating on diverse fuels such as gasoline, diesel and kerosene.
2. Description of the Prior Art
The U.S. Army has used Lenoir cycle pulsejet combustion engines in smoke generator systems since the 1940s. Lenoir cycle engines are constant volume, pistonless engines. The operation of a conventional Lenoir cycle engine used in Army smoke generators is as follows: (1) a compressed air charge and gasoline are sprayed into the engine head causing the petal valves in the head to open so that the air-fuel charge can enter the combustion chamber; (2) a spark plug in the combustion chamber ignites the mixture, and the explosion closes the petal valves and the "pulse" travels down a tube to provide heat (for the vaporization of fog oil in Army smoke generator systems); and (3) as the pulse leaves the combustion chamber a low pressure area is induced which opens the petal valves and allows the next air-fuel charge to enter the combustion chamber to be ignited. After a few seconds of operation, the combustion chamber is hot enough to ignite the air-fuel charge without using a spark. A properly operating Lenoir cycle pulsejet will produce 60 explosions per second. The Army uses such engines to burn gasoline to produce heat which is then used to vaporize fog oil thereby producing a visual obscurant smoke cloud. Such clouds are used for defensive purposes on the battlefield.
All previous Lenoir cycle pulsejet combustion engines could only operate using gasoline as the fuel source. Because Lenoir cycle engines are pistonless constant volume engines, the ability to ignite the fuel in a cold engine is dependent upon the flashpoint temperature of the fuel being used. Therefore, gasoline has always been used in the Army's Lenoir cycle pulsejet combustion engines because gasoline has a very low flashpoint temperature and is, therefore, easy to ignite in a cold engine. However, this low flashpoint also translates into the fact that gasoline is very dangerous to store, dispense and use. For this reason, the Army has implemented a program to phase out gasoline and replace it with diesel or kerosene based fuels. However, since diesel and kerosene fuels have flashpoints much higher than gasoline, existing Lenoir cycle engines will not ignite these fuels.
The invention described herein modifies the conventional Lenoir cycle pulsejet combustion engine so that it can operate using gasoline, diesel, or kerosene based fuels despite the significant difference in flashpoint temperatures of such fuels. Because diesel and kerosene based fuels have much higher flashpoints they are safer to store, dispense and use. This provides for safer operation of Lenoir pulsejet engines in Army smoke generator systems and improves the applicability of such engines to fields such as home heating systems. Moreover, the present invention provides the potential of multifuel use in combustion engines in general, and is not limited in application to Lenoir cycle pulsejet combustion engines.